U.S. patent number 11,351,975 [Application Number 16/385,738] was granted by the patent office on 2022-06-07 for hybrid-electric vehicle plug-out mode energy management.
This patent grant is currently assigned to Ford Global Technologies, LLC. The grantee listed for this patent is FORD GLOBAL TECHNOLOGIES, LLC. Invention is credited to Rajit Johri, Ming Lang Kuang, Wei Liang, Ryan Abraham McGee, Xiaoyong Wang, Mark Steven Yamazaki.
United States Patent |
11,351,975 |
Liang , et al. |
June 7, 2022 |
Hybrid-electric vehicle plug-out mode energy management
Abstract
A vehicle includes an engine, an electric machine, a battery,
and at least one controller. The vehicle may further comprise a
port for supplying power to a load external to the vehicle. The
controller is programmed to operate the engine at a power level
based on a difference between a battery voltage and a reference
voltage such that a power output by the electric machine reduces
the difference. The power level may define an engine operating
point that minimizes fuel consumption. The operating point may be
an engine torque and an engine speed. The power level may be
further based on a state of charge of the battery. The electric
machine may be operated to cause the engine to rotate at an engine
speed corresponding to the selected power level. The difference may
be caused by varying power drawn by a load external to the
vehicle.
Inventors: |
Liang; Wei (Farmington Hills,
MI), Yamazaki; Mark Steven (Canton, MI), Wang;
Xiaoyong (Novi, MI), Johri; Rajit (Ann Arbor, MI),
McGee; Ryan Abraham (Ann Arbor, MI), Kuang; Ming Lang
(Canton, MI) |
Applicant: |
Name |
City |
State |
Country |
Type |
FORD GLOBAL TECHNOLOGIES, LLC |
Dearborn |
MI |
US |
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Assignee: |
Ford Global Technologies, LLC
(Dearborn, MI)
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Family
ID: |
1000006355036 |
Appl.
No.: |
16/385,738 |
Filed: |
April 16, 2019 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20190241171 A1 |
Aug 8, 2019 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14057048 |
Apr 16, 2019 |
10259443 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60L
58/20 (20190201); B60W 10/08 (20130101); B60L
15/20 (20130101); B60L 50/66 (20190201); B60L
1/006 (20130101); B60W 30/18054 (20130101); B60L
58/12 (20190201); B60L 1/02 (20130101); B60L
50/16 (20190201); B60W 20/13 (20160101); B60W
10/26 (20130101); B60W 10/06 (20130101); B60L
53/14 (20190201); B60L 2240/423 (20130101); B60W
2510/085 (20130101); B60L 2210/10 (20130101); B60L
2240/441 (20130101); B60L 2210/40 (20130101); B60L
2270/142 (20130101); Y02T 10/62 (20130101); B60L
2240/421 (20130101); B60L 2240/12 (20130101); B60L
2240/427 (20130101); Y02T 10/70 (20130101); B60L
2240/549 (20130101); B60L 2240/425 (20130101); B60L
2240/545 (20130101); B60L 2240/527 (20130101); B60L
2210/30 (20130101); Y02T 10/72 (20130101); Y02T
10/7072 (20130101); B60L 2260/22 (20130101); B60L
2270/145 (20130101); Y10S 903/93 (20130101); B60L
2240/443 (20130101); Y02T 90/14 (20130101); Y02T
90/12 (20130101); Y02T 10/64 (20130101); B60L
2240/429 (20130101); B60L 2270/12 (20130101); Y02T
90/40 (20130101); B60W 2710/244 (20130101); B60L
2240/547 (20130101) |
Current International
Class: |
B60W
10/06 (20060101); B60L 1/02 (20060101); B60L
15/20 (20060101); B60W 10/26 (20060101); B60L
53/14 (20190101); B60L 50/16 (20190101); B60L
58/12 (20190101); B60L 58/20 (20190101); B60L
50/60 (20190101); B60W 10/08 (20060101); B60W
30/18 (20120101); B60L 1/00 (20060101); B60W
20/13 (20160101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2004104936 |
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Apr 2004 |
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JP |
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2004104936 |
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Apr 2004 |
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JP |
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2006180658 |
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Jul 2006 |
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JP |
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4104940 |
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Apr 2008 |
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JP |
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4104940 |
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Jun 2008 |
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JP |
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4353093 |
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Aug 2009 |
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JP |
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4353093 |
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Oct 2009 |
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JP |
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WO-2009158224 |
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Dec 2009 |
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WO |
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Other References
Chinese Patent Office, First Office Action for the corresponding
Chinese Patent Application No. 201410557739.2, dated Nov. 29, 2017.
cited by applicant.
|
Primary Examiner: Chen; Shelley
Attorney, Agent or Firm: Kelley; David B. Brooks Kushman
P.C.
Parent Case Text
REFERENCE TO RELATED APPLICATIONS
This application is a division of U.S. application Ser. No.
14/057,048 filed Oct. 18, 2013, now U.S. Pat. No. 10,259,443 issued
Apr. 16, 2019, the disclosure of which is hereby incorporated in
its entirety by reference herein.
Claims
What is claimed is:
1. A vehicle comprising: an engine; an electric machine
mechanically coupled to the engine and electrically coupled to a
high-voltage bus; and at least one controller programmed to, in
response to a difference between a voltage associated with the
high-voltage bus and a reference voltage in the absence of a demand
for propulsive power, operate the engine at a target torque and
operate the electric machine at a torque that drives a speed of the
engine to a target speed and generates power on the high-voltage
bus at a level to reduce the difference.
2. The vehicle of claim 1 wherein the level corresponds to a
predetermined engine operating point that defines the target speed
and the target torque.
3. The vehicle of claim 1 wherein the voltage associated with the
high-voltage bus is a terminal voltage of a traction battery that
is coupled to the high-voltage bus.
4. The vehicle of claim 3 wherein the level is further defined to
maintain a state of charge of the traction battery.
5. The vehicle of claim 3 wherein the level is further defined to
charge the traction battery to a predetermined state of charge.
6. The vehicle of claim 1 further comprising a port electrically
coupled to the high-voltage bus and configured to provide power
from a traction battery coupled to the high-voltage bus or the
electric machine to an external load electrically connected
therewith.
7. The vehicle of claim 6 wherein the voltage associated with the
high-voltage bus is a voltage measured at the port.
8. The vehicle of claim 1 wherein the level corresponds to a
predetermined engine operating point that generally minimized fuel
consumption of the engine.
9. The vehicle of claim 1 wherein the torque is based on an error
between target speed and an actual speed of the engine.
10. The vehicle of claim 1 wherein the difference changes as an
external load coupled to the high-voltage bus via a port draws
power from the high-voltage bus.
Description
TECHNICAL FIELD
This application relates to control of a hybrid vehicle powertrain
to provide power to external devices.
BACKGROUND
Hybrid vehicles combine traditional fuel-powered engines with
electric motors to improve fuel economy. To achieve better fuel
economy, a hybrid vehicle includes a traction battery that stores
energy for use by the electric motors. During normal operation, the
state of charge of the battery may fluctuate. The battery may be
charged by controlling the engine and a generator to provide power
to the battery. Additionally, a plug-in hybrid may recharge the
battery by plugging in to an external power supply.
A hybrid vehicle may also be adapted to provide power to loads
external to the vehicle. The vehicle may have a plug-out mode where
an external load can be connected to the vehicle. In the plug-out
mode, the vehicle provides power to the external load. One possible
application may be to provide electrical power to a house as a
backup generator. For example, the vehicle power bus may be
connected to an external inverter that converts DC voltage to an AC
voltage compatible with household devices. The traction battery may
provide the power or the engine may be operated to drive a
generator to provide the external power.
SUMMARY
A vehicle includes an engine, a battery with terminals, and an
electric machine. The vehicle further includes at least one
controller programmed to, in response to a difference between a
voltage across the terminals and a reference voltage in the absence
of a demand for propulsive power, operate the engine at an
operating point selected based on the difference such that a power
output by the electric machine reduces the difference. The
operating point may be selected such that, for the power output by
the electric machine, fuel consumption by the engine is generally
minimized. The operating point may define a torque command and a
speed command for the engine. The operating point may be further
selected based on a state of charge of the battery such that the
power output by the electric machine generally maintains the state
of charge of the battery. The operating point may be further
selected based on a state of charge difference between a state of
charge of the battery and a predetermined state of charge such that
the power output by the electric machine reduces the state of
charge difference. The at least one controller may be further
programmed to operate the electric machine to cause the engine to
rotate at an engine speed defined by the operating point.
A vehicle includes an engine, and an electric machine mechanically
coupled to the engine and electrically coupled to a traction
battery. The vehicle further includes at least one controller
programmed to, in response to a difference between a voltage
associated with the traction battery and a reference voltage in the
absence of a demand for propulsive power, operate the engine to
drive the electric machine to output power at a level sufficient to
reduce the difference such that fuel consumed by the engine is
generally minimized for the level. The level may correspond to a
predetermined engine operating point. The voltage associated with
the traction battery may be a terminal voltage of the traction
battery. The level may be further sufficient to maintain a state of
charge of the traction battery. The level may be further sufficient
to charge the traction battery to a predetermined state of charge.
The vehicle may further include a port electrically coupled to the
traction battery and configured to provide power from the traction
battery or the electric machine to an external load electrically
connected therewith. The voltage associated with the traction
battery may be a voltage measured at the port.
A method of controlling a vehicle by at least one controller
includes selecting a power level for an electric machine based on a
difference between a voltage of a high-voltage bus and a reference
voltage. The method further includes selecting an operating point
for an engine that generally minimizes fuel consumption at the
selected power level. The method further includes operating the
engine at the operating point to drive the electric machine to
produce the selected power to reduce the difference. The selected
power level may further maintain a state of charge of a traction
battery electrically connected to the high-voltage bus. The
selected power level may further drive a state of charge of a
traction battery electrically connected to the high-voltage bus to
a predetermined state of charge. The selecting and operating may be
performed in the absence of a demand for propulsive power.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a diagram of a plug-in hybrid-electric vehicle
illustrating typical drivetrain and energy storage components.
FIG. 2 is a diagram illustrating a possible control scheme for
providing power to an external load.
FIG. 3 is a plot illustrating the optimal operating point of the
engine.
FIG. 4 is a flowchart illustrating a possible implementation of
providing power to an external load.
DETAILED DESCRIPTION
Embodiments of the present disclosure are described herein. It is
to be understood, however, that the disclosed embodiments are
merely examples and other embodiments can take various and
alternative forms. The figures are not necessarily to scale; some
features could be exaggerated or minimized to show details of
particular components. Therefore, specific structural and
functional details disclosed herein are not to be interpreted as
limiting, but merely as a representative basis for teaching one
skilled in the art to variously employ the present invention. As
those of ordinary skill in the art will understand, various
features illustrated and described with reference to any one of the
figures can be combined with features illustrated in one or more
other figures to produce embodiments that are not explicitly
illustrated or described. The combinations of features illustrated
provide representative embodiments for typical applications.
Various combinations and modifications of the features consistent
with the teachings of this disclosure, however, could be desired
for particular applications or implementations.
FIG. 1 depicts a typical hybrid-electric vehicle (HEV). A typical
hybrid-electric vehicle 12 may comprise one or more electric
machines 14 mechanically connected to a hybrid transmission 16. The
electric machines 14 may be operable as a motor and a generator. In
addition, the hybrid transmission 16 is mechanically coupled to an
engine 18. The hybrid transmission 16 may also be mechanically
coupled to a drive shaft 20 that is mechanically coupled to the
wheels 22. The electric machines 14 may provide propulsion and
deceleration capability when the engine 18 is turned on or off. The
electric machines 14 may act as generators and can provide fuel
economy benefits by recovering energy that would normally be lost
as heat in the friction braking system. The electric machines 14
may also provide reduced pollutant emissions since the hybrid
electric vehicle 12 may be operated in an all-electric mode under
certain conditions.
In certain modes of operation, at least one of the electric
machines 14 may act as an onboard generator. The shaft of the
electric machine 14 may be driven by the engine 18, either directly
or through the hybrid transmission 16. The power output of the
engine 18 is a function of the engine torque and the engine speed.
The mechanical energy created by the engine 18 may be converted to
electrical energy through the electric machine 14 acting as a
generator. The power output by the electric machine 14 is a
function of the electric machine speed and the electric machine
torque.
The battery pack 24 stores energy that can be used by the electric
machines 14. A vehicle battery pack or traction battery 24
typically provides a high voltage DC output. A high-voltage bus 40
may be defined for connecting loads requiring high-voltage. The
battery pack 24 may be electrically coupled to the high-voltage bus
40 to provide power to and receive power from the high-voltage bus
40. The high-voltage bus 40 may represent a connection point for
loads that require a connection to high-voltage power. One or more
power electronics modules 26 may be electrically connected to the
high-voltage bus 40 and may be configured to provide power to and
receive power from the high-voltage bus 40. The power electronics
module 26 may be electrically connected to the electric machines 14
and provides the ability to bi-directionally transfer energy
between the high-voltage bus 40 and the electric machines 14. For
example, a typical battery pack 24 may provide a DC voltage while
the electric machines 14 may require a three-phase AC current to
operate. The power electronics module 26 may convert the DC voltage
to a three-phase AC current as required by the electric machines
14. In a regenerative mode, the power electronics module 26 may
convert the three-phase AC current from the electric machines 14
acting as generators to the DC voltage required by the battery pack
24.
In addition to providing energy for propulsion, the battery pack 24
may provide energy for other vehicle electrical systems. A typical
system may include a DC/DC converter module 28 that converts the
high-voltage DC output of the battery pack 24 to a low-voltage DC
supply that is compatible with other vehicle loads. The DC/DC
converter module 28 may be electrically connected to the
high-voltage bus 40 and be configured to provide power to and
receive power from the high-voltage bus 40. Other high-voltage
loads, such as compressors and electric heaters, may be connected
directly to the high-voltage bus 40. In a typical vehicle, the
low-voltage systems are electrically connected to an auxiliary
battery (e.g., 12V) 30. The auxiliary battery 30 is depicted as a
12V battery but may be at any voltage suitable for the particular
application (e.g., 24V, 48V, etc.). An all-electric vehicle may
have a similar architecture but without the engine 18 and a
modified transmission 16.
The vehicle may be a plug-in HEV in which the battery pack 24 may
be recharged by an external power source 36. The external power
source 36 may provide AC or DC power to the vehicle 12 by
electrically connecting through a charge port 34. The charge port
34 may be any type of port configured to transfer power from the
external power source 36 to the vehicle 12. The charge port 34 may
be electrically connected to a power conversion module 32. The
power conversion module 32 may condition the power from the
external power source 36 to provide the proper voltage and current
levels to the battery pack 24. In some applications, the external
power source 36 may be configured to provide the proper voltage and
current levels to the battery pack 24 and the power conversion
module 32 may not be necessary. The functions of the power
conversion module 32 may reside in the external power source 36 in
some applications.
One or more controllers may be present in the vehicle to control
the operation of the various components. A Vehicle System
Controller (VSC) 44 is shown as part of the vehicle. Other
controllers are not shown in the figures. The controllers may
communicate with one another in any appropriate manner. A
communications bus may be a wired connection that connects the
controllers of the vehicle 12 such that the data may be transmitted
and received between controllers. The communications bus may be a
serial bus, such as a controller area network (CAN). Communications
may also be via discrete hardware signals between controllers. A
combination of serial and discrete communication signals may also
be utilized.
For example, the various components within the vehicle may each
have an associated controller. The engine 18 may have an associated
controller to control and manage operation of the engine 18. The
engine controller may monitor signals associated with the engine 18
such as engine speed and engine torque. The engine controller may
control various aspects of the engine 18 operation.
The transmission 16 may have an associated controller to control
and manage operation of the transmission 16. The transmission
controller may monitor signals associated with the transmission 16
such as transmission output speed, fluid level, and gear positions.
The transmission controller may control various aspects of the
transmission 16 operation.
The Power Electronics Module 26 may have an associated controller
to control and manage operation of the module and the electric
machines 14. The power electronics controller may monitor signals
associated with the electric machines 14, such as speed, current,
voltage, and temperature. The power electronics controller may also
monitor signals associated with the power electronics such as the
DC bus voltage. The power electronics controller may also control
various aspects of the electric machine 14 operation.
The battery pack 24 may have an associated controller to manage and
control the operation of the battery pack 24. The battery
controller may monitor signals associated with the battery pack 24,
such as battery voltage, battery current, and battery temperature.
The battery controller may control various aspects of the battery
pack 24 operation.
The vehicle may have at least one controller 44 to manage and
control the operation of the various components. The controller may
be a Vehicle System Controller (VSC) 44. The VSC 44 may be
connected to other controllers via a communications bus (not
shown). The VSC 44 may coordinate the operation of the other
controllers to achieve vehicle level objectives.
In addition to providing power for propulsion of the vehicle 12,
the battery pack 24 may be configured to provide electric power to
an external load 42. The external load 42 may be equipment that is
off-board the vehicle or may be equipment that is on the vehicle.
The external load 42 may be external to the hybrid powertrain. For
example, the external load 42 could be a device that is carried by
or attached to the vehicle 12 that requires power to be provided by
the vehicle 12. This mode of operation is referred to as a plug-out
mode of operation. In this mode, energy may be provided for
external uses by plugging into the high voltage bus 40 of the
vehicle. The engine 18 and electric machine 14 operated as a
generator may also be used to provide power from the vehicle 12 in
the absence of a demand for propulsive power.
The vehicle 12 may have a plug-out connector module 38 that may
enable connection to the high-voltage bus 40. The plug-out
connector module 38 may be controlled by a controller such as the
VSC 44. The plug-out connector module or port 38 may control the
delivery of high-voltage to the external load 42. The plug-out
connector module 38 may enable and disable high voltage that is
passed to the external load 42. The plug-out connector port 38 may
have the capability to selectively connect high voltage from the
high-voltage bus 40 to the external load 42. The plug-out
connection port 38 may provide a connection point for connecting
the external load 42 to the vehicle 12. The port 38 may provide
connections for high voltage and for communications between the
vehicle 12 and the external load 42. The plug-out connector port 38
may provide an indication to other controllers that an external
load 42 is connected to the vehicle 12.
In a plug-out mode of operation, the vehicle 12 may be stationary.
The engine 18 may be running to power the electric machine 14
acting as a generator. The following description is based on
operating the electric machine 14 as a generator, so the term
generator may be used interchangeably with the term electric
machine 14 in the following description. The hybrid powertrain may
be designed such that one or more of the electric machines 14 may
be operated as a generator while the vehicle 12 is stationary. The
electric machine 14 operating as a generator converts the
mechanical power of the engine 18 into electrical power. The
high-voltage bus 40 may be connected to an external device 42
through the plug-out connector port 38. For example, the external
load 42 may be an external inverter that converts the DC bus
voltage to an AC voltage for driving AC accessories. This mode of
operation may require control of the engine 18 and electric machine
14. It may be important to control the on-board components to match
the power requirements of the external load 42. Important
considerations for the control may be robustness to load variations
and fuel efficiency. Such a system should maintain the battery
state of charge for driving purposes as well as provide sufficient
power to the external loads. The issue becomes one of how to
control the engine and generator to provide power to a varying
external load in the most fuel efficient manner.
FIG. 2 outlines the various functions that a plug-out mode energy
management controller may perform. The functions described may be
implemented by one or more of the controllers in the vehicle. One
function may be to calculate a generator power request for
maintaining the battery state of charge (SOC) 60. The generator
power request 64 may be an amount to power to request from the
electric machine 14 operating as a generator. The generator power
request 64 may be configured to maintain the battery state of
charge at a desired level. When the battery state of charge falls
below a predetermined value, a request to provide power may be
determined. If the battery state of charge is above a predetermined
value, a request to provide power from the engine may not be
necessary. The generator power request 64 may also be configured to
increase or decrease the battery state of charge to a predetermined
state of charge value.
To determine the power required to maintain the state of charge at
a given level, the present state of charge (SOC) may be input 62.
The power required to maintain a particular state of charge may be
determined based on test data or analysis. The power required to
maintain the battery SOC may take into account the base amount of
power required when all necessary modules are powered on to operate
in the plug-out mode of operation. A table or equation may be used
to calculate a base output power for maintaining the state of
charge, P.sub.g.sup.ref 64, at a desired level. The desired SOC
level to maintain may be the present SOC level. It may also be
desired to set the SOC level to be within an optimal range for the
battery, in which case, the power output may be set to increase or
decrease battery SOC accordingly. The base output power for
maintaining the battery state of charge, P.sub.g.sup.ref 64, may
also be based on a difference between the current battery state of
charge 62 and a predetermined state of charge set point.
In a case where an external load is connected, the power required
by the load 92 may not be known. The power requirement of the
external load, P.sub.Load 92, may vary depending on how the
external load is operated. It may be desired to adjust the base
power level 64 to maintain the battery SOC according to the power
drawn by the external load. The base output power, P.sub.g.sup.ref
64, may be adjusted for bus voltage variations to account for
variations in the external load power 92. A bus voltage
compensation value 68 may be subtracted from the base output power,
P.sub.g.sup.ref 64, to determine an adjusted output power level,
P.sub.g.sup.des 66. The adjusted output power level 66 may be a
power value that is required to satisfy the total power
demands.
The engine 18 and generator 14 may be controlled to provide power
to the battery pack 24 to maintain the state of charge at a desired
level. If the battery SOC is above a predetermined value, it may be
desirable to provide the external power requirements from the
battery pack 24. In this mode, the engine 18 may be turned off
until such time as the battery pack 24 needs to be charged. If the
battery SOC is below a threshold, it may be desirable to command
generator power to increase the SOC to a desired level. The engine
18 may be operated to always provide power when an external load is
connected so that battery SOC is not reduced.
A suitable operating point for the engine 18 and generator 14 may
be determined. The desired generator power level, P.sub.g.sup.des
66, may be used as an input to determine a desired engine operating
point 68. Determination of the engine operating point may require
that engine power losses be added to the desired generator power
level 66 to compensate for inefficiencies of the engine 18. That
is, for a given output power of the generator, the engine may have
to provide more power to compensate for mechanical losses of the
engine. Additionally, power losses within the power electronics
module 26 and the generator 14 may be considered when determining
the engine operating point. The engine operating point may be one
that minimizes fuel consumption for the given generator power
level. The operating point may be defined by a target engine speed,
.omega..sub.e* 70, and a target engine torque, .tau..sub.e* 72.
When the vehicle is parked and not moving, the engine 18 and
generator 14 speeds may be decoupled from the vehicle speed. The
engine 18 and generator 14 may be operated at any speed that is
allowed by performance constraints (e.g., noise, vibration, and
harshness (NVH) constraints). The operating point of the engine 18
and the generator 14 may be selected to minimize fuel consumption
of the engine 18. Selection of the engine 18 operating point may
take into account the efficiency of the generator 14 and the engine
18.
As the desired output power 66 changes, the operating point may
move along an optimal efficiency curve 162 as shown in FIG. 3. The
curve shown may be one that optimizes fuel consumption. As an
example, the engine may be operating presently at an engine power
level, P.sub.e 150, defined by torque level, T.sub.1 154, and
engine speed level, .omega..sub.1 156. If the required external
load power increases, the engine power level may be increased to
support the external load. As the adjusted output power level,
P.sub.g.sup.des (66 FIG. 2) increases, the power requirement of the
engine may increase by an amount .DELTA.P.sub.e. The system may
find a new operating point 152 on the optimal efficiency curve 162
that reflects the new required output power level.
If the system is not generating enough power to support the
external load, the battery voltage may decrease below a
predetermined reference voltage. Referring to FIG. 2, an error 102
between a reference voltage 96 and the battery voltage 94 may be
calculated as the difference between the reference voltage 96 and
the battery voltage 94. The error 102 may be used to calculate a
power adjustment, .DELTA.P.sub.g 68, that adjusts the power level
to provide the external load power. When the battery voltage 94 is
below the reference voltage 96, the power adjustment,
.DELTA.P.sub.g 68, may cause an increase in the adjusted output
power level, P.sub.g.sup.des 66.
The engine power required for a given required generator power may
be determined by estimating power losses of the system. A new
engine power may be calculated based on the desired generator power
level 66. The new engine power may be represented as the sum of the
previous engine operating power and a change in engine power,
.DELTA.P.sub.e. The engine power calculation may take into account
factors such as engine efficiency, electric machine losses, and
electrical transmission losses. Referring to FIG. 3, the new engine
power value may be used to generate a new operating point 152. The
new operating point 152 may be defined by a torque level, T.sub.2
158, and engine speed level, .omega..sub.2 160. Note that since
power is the product of torque and speed, there are many possible
combinations that could supply the required change, .DELTA.P.sub.e,
however, only one such point may exist on the optimal curve 162.
The combination selected may be optimized based on specific
criteria to minimize fuel consumption of the engine. The engine
operating point may be implemented as a predetermined table of
values indexed by the desired generator power output.
Referring again to FIG. 2, once an engine operating point (70, 72)
is selected, the engine 18 and generator 14 may be controlled to
this operating point. The engine 18 may be operated in an engine
torque control mode where the engine torque output 76 may be
controlled. The engine control 74 may control the engine torque,
.tau..sub.e 76, to the target value, .tau..sub.e* 72 using various
methods. The engine torque 76 may be adjusted by controlling a
throttle position, a spark retard, or valve timing represented by
signal 104. The engine control function 74 may send control signals
104 to the appropriate devices associated with the engine 18 to
control the engine 18 operation. The expected result is that the
engine will supply a torque 76 to the engine crankshaft.
The generator torque output 78 may be controlled by operating the
generator 14 in a speed control 80 mode. In a speed control mode of
operation, the electric machine torque 78 may be varied to maintain
a target engine speed 70. The engine speed and generator speed may
be related by a gear ratio. Knowing the engine speed or the
generator speed allows the other speed to be calculated. The engine
speed may be measured using a sensor on the engine shaft. The
generator speed may be measured using a speed sensor on the
generator shaft.
For example, an increase in applied engine torque 76 may rotate the
engine shaft which may tend to increase the engine speed and the
generator speed. The generator torque 78 will tend to counteract
the engine torque to prevent the engine speed 84 from straying from
the target speed 70. The effect is that the generator torque,
.tau..sub.g 78, will balance the engine torque, .tau..sub.e 76, to
maintain the target engine speed 70. The generator torque,
.tau..sub.g 78, may be negative when the engine is producing a
positive output power. The speed control 80 may operate by
adjusting the generator torque, .tau..sub.g 78, based on an error
114 between the commanded engine speed, .omega..sub.e* 70, and the
actual engine speed, .omega..sub.e 84. Alternatively, the commanded
engine speed may be converted to a commanded generator speed to
generate an error signal in conjunction with the generator speed
84. The generator torque, .tau..sub.g 78, may additionally be
adjusted based on an error between a commanded generator torque and
the actual generator torque. A proportional and integral (PI) type
of control may be used in the speed controller 80. Additional types
of controllers may be used with or instead of the PI control to
improve the transient speed control behavior or to satisfy other
system requirements.
The generator speed control may output a generator torque
reference, .tau..sub.g 108. The generator torque reference 108 may
be processed by the power electronics module 26 to control the
generator current 110. The generator 14 may provide a torque 78
that is ideally equal to the generator torque reference 108.
The system may respond to the engine torque 76 and generator torque
78 based on the particular characteristics of the system. The
engine-generator dynamics 82 will determine the actual response to
the torque inputs. The engine speed, .omega..sub.e 84, will vary
based on the sum of the engine torque, .tau..sub.e 76, and the
generator torque, .tau..sub.g 78. Generally, the engine speed 84
will increase as the net torque applied 112 (sum of engine torque
76 and generator torque 78) is increased.
The power provided by the engine, P.sub.e 86, may be expressed as
the product of the engine torque, .tau..sub.e 76, and the engine
speed, .omega..sub.e 84. Since there are losses in the engine due
to friction and other loads required to operate the engine 18, the
total electrical power generated, P.sub.g 90, may be the engine
power, P.sub.e 86 reduced by the additional loads and losses,
P.sub.loss 88. The losses may also include the efficiency of the
generator 14 and power distribution system. The generated
electrical power may provide power to the external electrical load,
P.sub.load 92, and to the battery 24 to maintain the battery state
of charge. The net power left 106 for the battery is the difference
between the generated electrical power, P.sub.g 90, and the power
used by the external load, P.sub.load 92.
The power supplied to or provided by the battery pack 24 may affect
the battery voltage, V.sub.batt 94. Power supplied to the battery
24 may generally increase the battery voltage 94, while power
provided by the battery 24 may generally decrease the battery
voltage 94. The change in battery voltage 94 provides a mechanism
to determine if the system is operating sufficiently to provide
power to the external load.
The power supplied may be compensated for bus voltage variations.
The external accessory power load 92 required to be provided by the
generator system may be unknown. When the load power 92 is
increased, more current will be drawn from the high-voltage bus and
the bus voltage 94 may drop. To adapt to this variation of power
usage, the desired generator output power 66 may be increased until
the electric machine 14 can provide enough power so that the bus
voltage 94 is maintained at a desired level. The feedback power
adjustment 68 can be fed back and combined with the base power
request 64. A reference voltage 96 may be subtracted from the
present battery voltage, V.sub.batt 94, to determine a voltage
error 102. A power adjustment, .DELTA.P.sub.g 68, may be calculated
from the voltage error 102. The power compensation 98 may be
accomplished by knowing the amount of current provided by or to the
battery 24. The power compensation 98 may be implemented as a table
or control algorithm within a controller. The power adjustment,
.DELTA.P.sub.g 68, may be fed back to determine the operating point
for the engine 18 and generator 14. In another example, the power
compensation 98 may be a PI controller that attempts to maintain
the battery voltage 94 at the reference value 96. In practice, many
control schemes may be utilized to implement the power compensation
98.
Once the power adjustment, .DELTA.P.sub.g 68, is determined, an
optimal operating point comprised of a desired engine torque 72 and
engine speed 70 combination can be found. An operating point may be
determined that lies on the optimal curve and defines an engine
torque 72 and engine speed 70 combination. The operating point may
be a point where the least fuel is used for a given power output.
Other optimization routines may be implemented as well.
The resulting operation is such that as the external power 92
demanded changes, the operating point of the engine 18 and
generator 14 is adjusted to provide power to the external load and
to maintain the battery voltage 94 at a given voltage 96. As the
power demanded by the external load 92 changes, the battery voltage
94 may increase or decrease in response. The change in battery
voltage 94 will cause the operating point of the engine 18 and
generator 14 to adjust in order to provide the desired power
requested 92 by the external load. An advantage of this
configuration is that the power demanded 92 by the external load
may be learned by the vehicle. There is no need for the external
load to communicate the required amount of power; therefore, any
external load may be connected so long as its power requirements
are within the limits that the vehicle can provide.
FIG. 4 shows an example of a flow chart for the control decisions
of operating the powertrain in a plug-out mode. The logic may be
implemented in a controller. A first check may be performed to
ensure that the vehicle is in a stationary condition 200. It may be
desired to ensure that there is no demand for propulsive power to
prevent vehicle movement while an external load is connected. This
may be done by monitoring a vehicle speed signal and/or the
transmission gear selector position. The controller may determine
the vehicle speed by monitoring one or more wheel speed sensors or
a transmission speed sensor. The vehicle may be required to be in a
park gear or mode to initiate or continue the plug-out mode. One or
more of an actual transmission gear and the status of a
transmission park mechanism may be monitored. In addition, the
plug-out connector module may have associated hardware to detect
that a plug is inserted. It may be important to detect that a
plug-out connector is inserted to prevent drive-off while providing
external power.
The system may then monitor to determine if the plug-out function
has been activated 202. This may be by a switch or other indicator
that the plug-out function is desired. Activation of the plug-out
function may be automatically detected when a load is connected to
the external port.
When the vehicle is stationary and in a parked condition and the
plug-out function is activated, the electric machine power output
level may be determined 204. An estimated power request may be
generated or received by the controller. The estimated power
request may be calculated to maintain the battery state of charge
at a predetermined value. The generator power output level may then
be adjusted based on deviations in the high-voltage bus voltage
from a desired high-voltage bus reference value.
When the generator power output is known, the engine power may be
calculated 206. The engine operating point may be optimized to
minimize at least one of fuel consumption, emissions, noise,
vibration, and harshness. The engine operating point may define an
engine torque and speed combination. Other optimization criteria
are possible.
The engine control logic may be commanded to the target engine
torque 208. The target engine torque may be communicated to an
engine control module to control the torque output by the engine to
the target engine torque by any available means. The engine control
function may produce actuator commands to cause the engine to
produce the requested amount of torque.
The electric machine speed control may be commanded to operate at a
target speed 210. The electric machine or engine speed may be
communicated to an electric machine speed control module to control
the electric machine speed to the target speed. A speed control
function may determine the appropriate electric machine torque to
maintain the speed set point.
The high-voltage bus voltage may be monitored 212 and compared to a
reference value 214. If the bus voltage is greater than a reference
voltage value, the power output may be decreased 216. If the bus
voltage is below the reference voltage value, the power output may
be increased 218. In this manner, the bus voltage attempts to
maintain a level near the reference voltage value.
An example of a control algorithm that can control a
hybrid-electric vehicle in a plug-out mode under a variable
electrical load is disclosed. The algorithm allows the HEV to be
operated in a plug-out mode with a variable electric system load.
The engine and electric machine system are operated at an optimum
point for system fuel efficiency in the plug-out mode. The bus
voltage is monitored and the power generation is controlled to
maintain the voltage to a reference value at variable system loads.
Battery state of charge is maintained while providing electric
power to the external load.
The processes, methods, or algorithms disclosed herein can be
deliverable to/implemented by a processing device, controller, or
computer, which can include any existing programmable electronic
control unit or dedicated electronic control unit. Similarly, the
processes, methods, or algorithms can be stored as data and
instructions executable by a controller or computer in many forms
including, but not limited to, information permanently stored on
non-writable storage media such as ROM devices and information
alterably stored on writeable storage media such as floppy disks,
magnetic tapes, CDs, RAM devices, and other magnetic and optical
media. The processes, methods, or algorithms can also be
implemented in a software executable object. Alternatively, the
processes, methods, or algorithms can be embodied in whole or in
part using suitable hardware components, such as Application
Specific Integrated Circuits (ASICs), Field-Programmable Gate
Arrays (FPGAs), state machines, controllers or other hardware
components or devices, or a combination of hardware, software and
firmware components.
While exemplary embodiments are described above, it is not intended
that these embodiments describe all possible forms encompassed by
the claims. The words used in the specification are words of
description rather than limitation, and it is understood that
various changes can be made without departing from the spirit and
scope of the disclosure. As previously described, the features of
various embodiments can be combined to form further embodiments of
the invention that may not be explicitly described or illustrated.
While various embodiments could have been described as providing
advantages or being preferred over other embodiments or prior art
implementations with respect to one or more desired
characteristics, those of ordinary skill in the art recognize that
one or more features or characteristics can be compromised to
achieve desired overall system attributes, which depend on the
specific application and implementation. These attributes may
include, but are not limited to cost, strength, durability, life
cycle cost, marketability, appearance, packaging, size,
serviceability, weight, manufacturability, ease of assembly, etc.
As such, embodiments described as less desirable than other
embodiments or prior art implementations with respect to one or
more characteristics are not outside the scope of the disclosure
and can be desirable for particular applications.
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